1. Field of the Invention
The present invention relates to a valve timing adjustment device for changing the timing of operation of at least one of an intake valve and an exhaust valve (hereinafter the "timing of operation" referred to as a "valve timing") of an internal combustion engine (hereinafter the "internal combustion engine" referred to as an "engine").
2. Description of the Related Art
In the past, as one example of a valve timing adjustment device for adjusting the valve timing of at least one of an intake valve and an exhaust valve of an engine, it has been known to employ the vane type mechanism such as disclosed in Japanese Unexamined Patent Publication (Kokai) No. 9-112223 to the part of the drive force transmission means transmitting the drive force from a drive shaft of the engine, that is, the crankshaft, to a driven shaft, that is, the camshaft.
In this vane type valve timing adjustment device, it is necessary to provide a stopper portion to limit the amount of relative rotation of the vane rotor with respect to the housing. When providing a stopper portion at a vane, however, there is the problem that an excessive stress acts on the vane when the stopper portion is contacted. In particular, in a state where the oil pressure is lost, it is necessary to transmit the drive torque of the camshaft by just the vane, so there is a decline in reliability due to the insufficient strength of the vane. In particular, when providing a plurality of vanes, since the widths of the vanes are limited, it is difficult to give sufficient strength to the vanes.